Motion System Design

Adjustable-speed drives' passport to Europe: The CE mark

Are you or your customers selling adjustable-speed drives alone or installed on equipment within the European Union.? If you are then you should know about these new directives

As of January 1, 1996, all relevant electrical apparatus to be sold within the 15-member European Union (EU) must carry the European CE (European Council) Mark. This certification indicates compliance with all relevant EC directives, one of which could be the 1989 EMC directive covering both the emission of electromagnetic noise and the immunity of equipment to such disturbances.

Compliance with EMC directive 89/336/EEC is important because the EU is a huge market consisting of over 400 million persons — more than 40% of the world market.

The need for certification

The EMC directive is a part of the European Council’s broad attempt to simplify the conflicting technical standards that impede free trade between borders in Europe. Currently, each European nation follows its own set of nationally recognized guidelines, making EMC and electrical safety compliance difficult for foreign marketers. The European Council hopes to rectify the problem by gradually phasing in the CE marking system, which recognizes European Council approved technical directives. Each member EU nation must adopt these directives.

Scope of EMC directive

The EMC directive covers two aspects of electromagnetic noise: emissions and immunity. Electrical noise emission includes not only radiated noise (RFI) from electrical apparatus and cabling, but also noise conducted along supply lines.

Immunity refers to the susceptibility of electrical apparatus to conducted and radiated electrical noise.

Relevant apparatus. The EMC directive only applies to so-called “relevant” apparatus, not to electrical components such as resistors, switches or potentiometers. Electronic components such as ac and dc drive modules and systems are not relevant apparatus and should not be CE marked for the EMC directive. However, starting in 1997, they will need to be CE marked to indicate conformance to the low-voltage directive to demonstrate electrical safety.

The definition of relevant apparatus depends on the intended operation of the product and how it is marketed. For a product to qualify as relevant apparatus, it must first have the quality of intrinsic function, that is, it must have a dedicated purpose requiring no further modification by the end user.

Second, the supplier must supply the relevant apparatus directly to the end user.

Directive goals. The EMC directive has two basic goals. The first is to define acceptable RFI emission and immunity boundaries. These limits help determine, for instance, whether control equipment such as programmable logic controllers (PLCs) and personal computers (PCs) can operate near an ac inverter drive powered off the same supply mains. The second directive goal is to regulate the increased levels of RFI generated by the proliferation of electrical equipment in Europe to assure reliable telecommunications.

Who is responsible?

Whichever party — equipment manufacturer, OEM, or system integrator — imparts intrinsic function to the product, and sells it directly to an end user, has the responsibility for CE marking.

“Intrinsic function” criteria. A prepackaged unit (such as a pump speed controller) sold directly to an end user as a drive package has intrinsic function since the end user only needs to install the unit to be operational.

In this case, the drive manufacturer must treat the item as relevant apparatus, since it meets the intrinsic-function criterion and is sold directly to the end user. The manufacturer must take responsibility for testing and CE marking for EMC conformity, not as an independent module, but as the user will apply it—as a pre-packaged item including the drive, the enclosure and the mounted operator controls. Once the pre-packaged item is properly EMC tested, the manufacturer must:

1.Apply the CE mark to the product, product manual or documentation and issue a Declaration of Conformity
2.Provide EMC installation guidelines (usually with the product manual).
3.Until the emerging European Norm (EN) drive-specific standard (EN61800- 3) becomes law, include an ac supply filter compliant with EN50081, Part 1 or 2 (see box) depending on the operating environment.

OEM’s responsibility. Suppose a drive manufacturer sells ac inverters as component modules — without prepackaging — to an original equipment manufacturer (OEM) who then prepackages and markets them exclusively for stand alone, retrofit applications. The OEM has now made the leap from component to relevant apparatus. He now has the responsibility of EMC testing and CE marking the final, prepackaged product, since he has given the final product a specific intrinsic function and directly supplies it to the end user. The OEM must provide the same documentation, CE marking, filtering (if required) and installation guidelines that the manufacturer would otherwise provide.

Suppose a drive manufacturer sells a cubicle enclosure of three drives to a systems integrator who then configures the drives into a coordinated system for a slitter machine. The OEM builds and designs the slitter for resale to an end user and contracts with a systems integrator to configure the drives. Neither the drives manufacturer nor the systems integrator can take responsibility for CE marking the drives enclosure for the EMC directive. Rather, because the OEM provides the slitter machine with intrinsic function and sells the machine directly to the end user, he is left with the legal obligation to CE mark the entire machine.

A practical alternative for end users. In most cases, OEMs and system integrators design and build multiple-motor industrial drive systems to the tailored specifications of an end user. These systems are usually quite complex, involving many drives which interface with other types of industrial control equipment. CE certifying such large systems for the EMC directive can obviously be arduous and extremely expensive.

Fortunately, there is another way to bring drive systems into compliance. If an OEM designs and builds a machine or drive systems to the direct, custom specifications of an end user, who installs the system or contracts it out, then the EMC directive considers the final machine as “taken-into-service” by the end user. In these cases, the machine must meet the essential protection requirements of the 89/336/EEC directive only, and the machine, as a whole apparatus, should not be CE marked. EMC conformance responsibility lies with the end user who must meet only the essential protection requirements of the directive. This is a considerably less expensive and troublesome requirement than performing a complete conformance assessment for CE marking to EN standards.

In Europe for large systems in industrial environments, problems are dealt with on a case-by-case basis, or only if the generated RFI and EMI adversely affect the performance of the machine or other equipment. The end user, however, must take responsibility for developing an effective EMC plan. Filters are not mandatory and are installed only when problems occur. The taken-into-service option is the simplest and cheapest route to conformance and is much less onerous than CE marking the entire system, but it leaves the final EMC responsibility to the end user.

Notice that, although drive manufacturers have no legal obligation to ensure their drive modules meet the European Community’s EMC directive limits, they have a vested interest in providing distributors, systems integrators and OEM’s with drive modules that can comply. Any party responsible for getting the final product CE certified for EMC will always insist on drive modules which meet the EMC limits for their intended markets. Otherwise, the end user will force their suppliers to look elsewhere for a drive which does conform.

In all instances, the final supplier or end user takes responsibility for compliance to the EMC directive. More often than not, the end user will opt for a taken-into-service exclusion or insist on CE marking as a sales condition of the relevant apparatus, which relegates the CE marking task to the final supplier.

Paths to certification

There are two distinct routes for demonstrating conformance for drive systems and drive packages: self certification and maintaining a technical construction file, Figure 2. Self-certification requires suppliers to perform the EMC tests themselves, then issue a Declaration of Conformance. The party seeking EMC conformance must test only to applicable harmonized standards.

Testing, of course, requires time, expertise and expensive equipment. Most suppliers seeking conformance for drive products and systems do not have the facilities or the proper test equipment available in house. For this reason most drive manufacturers and suppliers hire outside testing facilities which is an expensive and lengthy process.

A more reasonable approach to demonstrating CE conformance with 89/336/EEC is to create a Technical Construction File (TCF). This TCF route is particularly appropriate for drive systems that control more than one motor (a slitter or a coating line, for instance, or a multiple drive system that includes a PLC). The supplier tests a drive product or system to the generic standards EN50081 and EN50082, or the draft version of the drive-specific standard (EN61800-3), and maintains a running file of all applicable test data. The file also details the technical arguments as to how and why the product complies with the EMC directive and must support any variance from emissions and immunity limits cited in EN61800-3 or the generic standards.

Once the tests are done and the file is complete, the supplier must then submit it for approval to a European Council authorized Competent Body. The Competent Body validates a TCFs test results and test methods and must agree with the technical rationale as to why the relevant apparatus is exempted from some tests. It may also request further testing.

Finding an approved Competent Body to validate a TCF can be difficult. Because a Competent Body must have outstanding capabilities in all areas of EMC, not just motor drives and motor drive systems, the European Council (through EN45011) sets strict requirements on qualifying a testing facility as a Competent Body. These certification requirements are not easy to meet, which explains why there are so few existing (approximately 80 in all of Europe).

To obtain more information

To obtain copies of the specifications, testing procedures, and other information about the CE Mark, contact: Press and Public Relations Delegation of the European Commission European Union 2300 M Street, NW Washington, D.C. 20037 Phone : 202-862-9500

The standards maze

The overall EMC directive is purposely broad covering nearly all electrical products aimed at the user and sold in Europe. It does not specify emission or immunity frequencies or power levels. Instead, the directive allows a party to demonstrate conformance by meeting the limits listed in evolving “harmonized” standards.

These standards attempt to coordinate existing national standards currently recognized by member nations within the EU. Each defines EMC limits for a distinct category of electrical apparatus.

Harmonized standards are distinct from their parent directives and can vary without having to revise the overall applicable directive. Technical committees charged with developing these standards report directly to the European Committee, which approves and publishes them in the Official Journal of the European Community. CE compliance is presumed if the product conforms to the applicable harmonized standards.

In principle, a harmonized, product-specific standard (or EN — European Norm) exists for each category of electrical products that defines the minimum EMC requirements for that category of electrical apparatus.

To indicate CE conformance with directive 89/336/EEC, the party responsible for CE marking must include a European Council Declaration of Conformity within the product documentation. This document serves as a legal attest to CE conformance and lists the harmonized standards to which the electrical device conforms. An officer or agent representing the responsible party or company must sign and date the document.

Generic standards. Since many productspecific standards—including a harmonized standard dedicated exclusively to governing EMC for ac and dc drives and drive systems—are still under development, manufacturers and sellers must apply a generic set of EMC standards. The Official Journal of the European Community is not expected to list this standard (slated to become EN61800-3) until January, 1997.

These generic standards include:

1. EN50081-1 EMC Generic Emission Standard, part 1—Residential, commercial and light industry environments.
2. EN50081-2 EMC Generic Emission Standard, part 2—Industrial environments.
3. EN50082-1 EMC Generic Immunity Standard, part 1—Residential, commercial and light industry environments.
4. EN50082-2 EMC Generic Immunity Standard, part 2—Industrial environments.

These define emission and immunity limits and clarify data necessary for proper compliance design and conformance testing.

Part 1 of each standard covers electrical equipment powered by a supply distribution system which directly powers residential, commercial or light industrial load customers.

Part 2 applies if the environment is considered strictly industrial in which case the supply is isolated from residential or commercial loads through a specifically dedicated distribution transformer system.

The RFI emission limits are more restrictive for electrical apparatus operating in residential, commercial or light-industrial environments because industrial electrical equipment produces higher noise interference levels which can propagate through power lines. By the same reasoning, the industrial generic immunity standard (part 2) has more restrictive immunity levels than the residential immunity standard.

Martin Payn, Ph.D., is the R &D conformance manager with Eurotherm Drives Ltd., Littlehampton, UK, and Michael F. Fekete is a technical writer, Eurotherm Drives Inc., Charlotte.

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